Packers are isolation devices that are mounted to a tubular mandrel. Some are set with compression of a sealing element external to the mandrel to reduce the length of the sealing element and increase its radial dimension. Other designs expand the mandrel from within to bring the sealing element to the borehole wall. Some designs employ swelling elements to bridge the gap to the borehole wall after exposure to well fluids over a period of time.
One recurring issue with packers is that they must be run into the well through a tubular with a drift dimension not much larger than the packer run in dimension and then the packer may have to be set in a much larger borehole. Packers with expandable mandrels have typically put the sealing element on the outside diameter of the mandrel leaving the sealing element exposed to damage during running in. US Publication 2010/0314130 puts the sealing elements on the mandrel outer diameter and uses a system of internal rings through which the swage has to pass to expand only at the seal locations with a resulting uniform internal diameter after expansion since the size of the swage is no larger than the drift diameter of the tubular being expanded.
Other designs place gripping members adjacent a sealing element and expand the mandrel from its interior. In this design the assembly is placed on the mandrel outer diameter which limits the initial internal dimension of the mandrel for run in which makes it more difficult to expand to a sealing condition in a larger wellbore. Such a design is illustrated in U.S. Pat. No. 7,117,949.
Other designs that are focused on using lighter wall pipe and giving it strength to resist collapse with a series of closely spaced corrugations make the claim that a sealing material can be deployed in the corrugations and a roller expander can be used to enlarge the corrugated segment with the sealing material for use as an isolation device. It claims protection for the sealing material during run in via the corrugations. The reality is that if the corrugations act as protection for a sealing material in a helical or circumferential groove then to try to get a seal with expansion will require elimination of the groove to even get the seal against the borehole wall. If that happens then the seal material will comprise of thin unsupported strips as the corrugations will be eliminated to even get sealing contact. The unsupported strips will roll on themselves and will not provide a reasonable annular seal. On the other hand if the corrugations are buried for run in then the sealing element is not protected for run in by the corrugations. Also a factor is that since the corrugations enable the use of thinner wall tubulars the expansion to the point of returning to parallel wall structure by flattening out all the corrugations will present a weaker mandrel that will have a fairly low differential pressure rating and may be too weak to retain the sealing element against the borehole wall in a sealing relationship. Such a design is illustrated in U.S. Pat. No. 7,350,584.
What is needed and provided by the present invention is an expandable packer that can have the element protected for run in while still be configured to sealingly be expanded to the surrounding wellbore. These features are addressed by projections on opposed ends of long recesses that hold the sealing element. The projections can extend radially upon expansion to act as anchors or extrusion barriers. A swelling material can optionally be used. Those skilled in the art will better understand the invention from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.